Powder bed fusion apparatus and methods

ABSTRACT

A powder bed fusion apparatus for building an object in a layer-by-layer manner includes a build platform movable within a build sleeve to define a build volume, a layer formation device for forming layers of powder across the build volume in a working plane and an irradiation device for irradiating powder in the working plane to selectively fuse the powder. The powder bed fusion apparatus further includes a mechanical manipulator arranged to engage with the object and/or a build substrate, to which the object is attached, to tilt the object in a raised position above the working plane such that powder is freed from the object and deposited at a location above the working plane and/or into the build volume.

This is a Continuation of application Ser. No. 16/483,263 filed Aug. 2,2019, which is a National Stage Application of PCT/GB2018/050435 filedFeb. 20, 2018, which in turn claims priority to British Application No.1702800.2 filed Feb. 21, 2017, British Application No. 1702801.0, filedFeb. 21, 2017, and European Patent Application No. 17195111.4 filed Oct.6, 2017. The entire disclosures of the prior applications are herebyincorporated by reference herein their entirety.

FIELD OF INVENTION

This invention concerns powder bed fusion apparatus and methods in whichselected areas of a powder bed are solidified in a layer-by-layer mannerto form a workpiece. The invention has particular, but not exclusiveapplication, to selective laser melting (SLM) and selective lasersintering (SLS) apparatus.

BACKGROUND

Powder bed fusion apparatus produce objects through layer-by-layersolidification of a material, such as a metal powder material, using ahigh energy beam, such as a laser or electron beam. A powder layer isformed across a powder bed contained in a build sleeve by lowering abuild platform to lower the powder bed, depositing a heap of powderadjacent to the lowered powder bed and spreading the heap of powder witha wiper across (from one side to another side of) the powder bed to formthe layer. Portions of the powder layer corresponding to a cross-sectionof the workpiece to be formed are then solidified through irradiatingthese areas with the beam. The beam melts or sinters the powder to forma solidified layer. After selective solidification of a layer, thepowder bed is lowered by a thickness of the newly solidified layer and afurther layer of powder is spread over the surface and solidified, asrequired. An example of such a device is disclosed in U.S. Pat. No.6,042,774.

A problem with such powder bed fusion apparatus is how to extract theworkpiece from the powder bed after completion of the build. Inparticular, it is desirable to extract the workpiece and recover theunsolidified powder without exposing the unsolidified powder to anatmosphere having a high oxygen concentration, for example air, suchthat the recovered powder can be used for a subsequent build. It isknown, for example, from EP1793979 to provide a glove box and suctionnozzle to allow a user to separate the powder from the workpiece beforethe workpiece is removed from the powder bed fusion apparatus. A problemwith such an apparatus is that it requires manual intervention through aglove box. It is desirable to provide an apparatus that can separate theworkpiece from the powder without manual intervention through a glovebox.

It is known from US2004/0084814 and US 2007/0026145 to provide one ormore gas inlet(s) and gas outlet(s) to the build sleeve to provide aflow of gas through the build sleeve for forcing powder from the buildsleeve.

US2008/0241404 describes apparatus comprising a build platform of thebuild sleeve having collapsible or removable parts capable of releasingunused powder directly from the build sleeve in a downward directionunder the force of gravity. Such a system is particularly unsuitable foruse with metal powder as a workpiece built from metal powder typicallymust be secured to a solid substrate plate, for example as described inU.S. Pat. No. 5,753,274.

Other systems separate the powder from the workpiece at a locationdifferent to that in which the workpiece is built. US2007/0001342 andWO2015/071184 disclose the removal of the build piston/container fromthe selective laser melting apparatus to a separate station in which thepowder is separated from the workpiece. US2007/0001342 describes astation comprising a tilting device with which the removed buildcontainer is tilted so that raising of a carrier pushes powder over anoverflow edge for collection. WO2015/071184 discloses a station in whichthe removed build container is rotated through an angle of at least 90degrees from an upright position. In an alternative embodiment, theconstruction platform may be already inserted into the rotary frameduring production of the object. The upright position from which theconstruction platform is rotated is that position of the constructionplatform in which the object has been produced.

DE102011002954 and US2001/0045678 discloses apparatus for transferringthe workpiece and powder bed to a powder removal station. US2001/0045678discloses transferring the workpiece to the powder removal stationthrough an opening in the build sleeve. DE102011002954 discloses raisingthe build platform such that the workpiece is elevated above the buildsleeve and then using a feed device for pushing the workpiece and powdercake into a filter device.

WO93/08928, US2015/0239177 A1 and WO2016/030530 A1 describe hat-likecontainers that are placed above the construction space, the containersopen on a side facing the construction space. The manufactured objectand non-solidified powder surrounding the object are displaced into thecontainer from the construction space. In WO93/08928 and US2015/0239177A1 the object and non-solidified powder are then removed from the devicewithin the container. US2015/0239177 A1 describes that the element thatserves as a base plate during layer-wise manufacturing is used as aclosure element for closing the container. In WO2016/030530 A1, the baseplate is a porous base plate and the container is linearly displaced tomove the porous base plate above a funnel shaped collecting containersuch that the powder surrounding the object falls from the hat-likecontainer into the collecting container.

A problem with such devices is that the unsolidified powder is eitherremoved from the powder bed fusion apparatus or the unsolidified powderis freed from the object and deposited away from the conventional powderhandling apparatus (dosing piston or powder overflow). Accordingly, forsuch a system there is a need to provide additional powder handlingand/or transport devices to recover the unsolidified powder for use in asubsequent build.

US2007/0126157 A1 discloses apparatus for recovering the powder into thebuild piston. The apparatus comprises ejector pins located in the buildpiston for pushing or pulling the part within the build piston to move aportion of the unbound powder away from the manufactured article. Toprovide space for the unbound powder to move, the build platform islowered further. This requires a stroke of the build piston that isgreater than the full build height. Furthermore, powder can still remaintrapped within the manufactured article.

SUMMARY OF INVENTION

According to a first aspect of the invention there is provided a powderbed fusion apparatus for building an object in a layer-by-layer manner,the powder bed fusion apparatus comprising a build platform movablewithin a build sleeve to define a build volume, a layer formation devicefor forming layers of powder across the build volume in a working plane,an irradiation device for irradiating powder in the working plane toselectively fuse the powder and a mechanical manipulator arranged toengage with the object and/or a build substrate, to which the object isattached, to tilt the object in a raised position above the workingplane such that powder is freed from the object and deposited at alocation above the working plane and/or into the build volume.

In this way, the freed powder can be recovered into the powder handlingdevices that are used in the build process, such as into a dosing pistonused for dosing powder to be spread by a wiper in the formation of alayer or into a powder overflow channel that is used to collect excesspowder at the end of layer formation. The powder may be deposited intosuch devices directly or may be transported into such devices using thebuild platform and/or a wiper used during the formation of the layers.In this way, additional complexity is avoided and a footprint of thepowder bed fusion and powder recovery apparatus can be reduced comparedto the prior art devices.

It will be understood that the “mechanical manipulator” is intended tobe limited to a mechanical device, i.e. a machine or machinery, but notnecessarily to a motorised and/or automated device. However, in apreferred embodiment, the mechanical manipulator is motorised such thatat least a proportion of the operations carried out by the mechanicalmanipulator are/can be automated. Alternatively, the mechanicalmanipulator may be operated through a manually applied force. Forexample, an external actuating rod or lever may be provided, whereinmanual manipulation of the actuating rod or lever operates themechanical manipulator.

The mechanical manipulator may be arranged to engage with the buildsubstrate supported on the build platform and on which the object isbuilt and attached, the mechanical manipulator arranged to tilt theobject by virtue of tilting the build substrate. The mechanicalmanipulator may be arranged such that, when engaged with the objectand/or build substrate, the object can be picked-up clear from the buildplatform. The object may comprise any feature built during the additivebuild process, such as a part or workpiece, one or more supports and/oranchors attaching the part or workpiece to the build substrate and/or afeature separate from the part or workpiece, for example an engagementfeature specifically built for engaging with the mechanical manipulator.The engagement feature may be built as an extension to thepart/workpiece or may be built on the build substrate separate from thepart/workpiece.

Unlike the typical build substrates, as disclosed in U.S. Pat. No.5,753,274, during the build, the build substrate may not be secured tothe build platform, for example by bolts or the like. In this way, themechanical manipulator can engage with the build substrate for tiltingof the build substrate without requiring an operation to free the buildsubstrate from the build platform.

Alternatively, the build platform and build substrate may be arrangedsuch that the build substrate can be releasably secured to the buildplatform such that, when the object and/or build substrate is engaged bythe mechanical manipulator, the build substrate to which the object isattached can be released from the build platform for titling of theobject without requiring manual access to the build substrate. Forexample, the build substrate and/or build platform may comprise anactuating mechanism for releasing a locking element that locks the buildsubstrate to the build platform. The mechanical manipulator may comprisethe actuating mechanism. Releasing of the build substrate from the buildplatform may be carried out automatically using a drive mechanism, suchas a motor or an electromagnet.

The mechanical manipulator may be arranged to invert the object, forexample by tilting the object by more than 90 degrees from an as builtorientation of the object and preferably, by 180 degrees. In this way,powder that may be otherwise trapped in the object may be freed. Themechanical manipulator may be arranged to rotate the object about two,preferably orthogonal, axes. Both axes may be non-orthogonal to theworking plane. Alternatively, a first one of the axes may benon-orthogonal to the working plane and a second one of the axessubstantially orthogonal to the working plane. The mechanicalmanipulator may be operable to tilt the object about the first axis whenthe mechanical manipulator is in at least two orientations about thesecond axis such that the object can be tilted about the first axis withthe object in different positions relative to the first axis. This mayhelp to free powder form internal channels/recesses in the object.

The mechanical manipulator may be mounted in the apparatus such that thebuild platform has to be lowered from an engagement position in whichthe mechanical manipulator engages with the object and/or buildsubstrate to provide room for rotation of the mechanical manipulatorengaged with the object and/or build substrate. For example, the buildplatform may be raised up the build sleeve to the engagement position,such as to a top of the build sleeve, to cause engagement of the objectand/or build substrate with the mechanical manipulator and then loweredback down the build sleeve to provide room for rotation of themechanical manipulator engaged with the object and/or build substrate.This may allow rotatable elements of the mechanical manipulator to bemounted for rotation about a fixed axis (e.g. fixed relative to thebuild sleeve) rather than having to move the axis away from the buildsleeve/build platform to provide sufficient clearance for rotation.

The powder bed fusion apparatus may comprise a build chamber formaintaining an inert atmosphere surrounding the object during the build,wherein the mechanical manipulator is arranged to tilt the object withinthe build chamber such that powder can be freed from the object whilstunder the inert atmosphere. This may be advantageous as oxidisation ofthe powder can result in undesirable effects, such as fires andexplosions and undesired properties of objects built in subsequentbuilds using the oxidised powder. By freeing the powder from the objectwhilst under the inert atmosphere oxidisation of the freed powder isavoided.

The mechanical manipulator may comprise a drive mechanism that extendsoutside of the build chamber, wherein application of a force to thedrive mechanism operates the mechanical manipulator. The drive mechanismmay be manually operable or driven by a motor.

Alternatively, the mechanical manipulator may be driven by an actuator,such as a motor, housed within the build chamber.

The mechanical manipulator may be arranged to remove the object from thebuild chamber. The mechanical manipulator may be mounted on a door ofthe build chamber, wherein opening of the door moves the mechanicalmanipulator and an object retained by the mechanical manipulator fromthe build chamber.

Alternatively, the mechanical manipulator may be mounted on a drivemechanism for withdrawing the mechanical manipulator and the retainedobject through a closable exit aperture in the build chamber. Theclosable exit aperture may be located in a ceiling of the build chamber.

The powder bed fusion apparatus may comprise a transfer chamber, whereinthe mechanical manipulator comprises a drive mechanism arranged formoving the object to the transfer chamber. The mechanical manipulatormay be located within the transfer chamber, the drive mechanism arrangedfor withdrawing the mechanical manipulator and the retained objectthrough a closable exit aperture into the transfer chamber, wherein theobject can be removed from the transfer chamber when the exit apertureis closed. The transfer chamber may be movable relative to the exitaperture, wherein movement of the transfer chamber closes the exitaperture. The irradiation device may comprise a scanner for directing aradiation beam to selected locations in the working plane, wherein thescanner is movable together with the transfer chamber such that thescanner closes the exit aperture when the transfer chamber moves awayfrom the exit aperture.

The transfer chamber may be an airlock chamber, wherein the object canbe removed from the build chamber through the transfer chamber whilstretaining the inert atmosphere in the build chamber.

The powder bed fusion apparatus may comprise a storage location outsideof the build chamber and the mechanical manipulator may be arranged to,preferably automatically, deposit the object in the storage location. Inthis way, the mechanical manipulator is free to process a subsequentobject built in the powder bed fusion apparatus without manualintervention. The mechanical manipulator may be arranged to, preferablyautomatically, pick-up a build substrate from the storage area for usein a subsequent build.

The mechanical manipulator may comprise at least one movable effectorfor engaging with the build substrate and/or object.

The effector may be at least one movable arm positionable such thatraising of the build platform is required for, and preferably, causes,the object and/or build substrate to be attached to the at least onearm, wherein subsequent movement of the at least one arm tilts theobject. The arm and build substrate may comprise cooperating fasteningelements that are engaged to attach the mechanical manipulator to thebuild substrate by raising of the build platform. The cooperatingfastening elements may comprise passive or active fastening elements.For example, the fastening elements may comprise passive fasteningelements in the form of a resilient element on one of the arm of themanipulator and the build substrate that is deflected by engagement of aflange on the other of the build substrate and the arm of themanipulator when the build platform is raised to cause the resilientelement to grip the flange, thus attaching the mechanical manipulator tothe build substrate. Active fastening elements may comprise fasteningelements activated by a motor or an electromagnet.

The mechanical manipulator may comprise a sensor for detectingengagement of the cooperating fastening elements. The mechanicalmanipulator may comprise an indicator for confirming engagement of thecooperating fastening elements, for example the indicator may beresponsive to detection of the engagement by the sensor.

The movable arm may be mounted for rotation about an axis that is notorthogonal to the working plane. The axis may be parallel with theworking plane. In this way, movement of the arm tilts the object.

The mechanical manipulator may comprise at least one first arm and atleast one second arm arranged such that one of the at least one firstarm and the at least one second arm can retain a first build substratebearing an object built in the powder bed fusion apparatus whilst theother one of the at least one first arm and the at least one second armretains a second build substrate for a subsequent build. The at leastone first arm and the at least one second arm may be mounted in a fixedrelationship such that the object on the first build substrate can betilted at the same time as locating the second substrate on the buildplatform. The mechanical manipulator may be arranged such that thesecond substrate can be released from the mechanical manipulator whilstthe first substrate remains retained in the mechanical manipulator. Inthis way, the build substrate for the next build can be put in place inparallel with a break-out of the current build from the unsolidifiedpowder.

The effector may comprise at least one finger movable under the controlof an actuator to engage an underside of the build substrate to tilt thebuild substrate, wherein the actuator and the finger are provided in oron the build platform.

The mechanical manipulator may comprise a powder guide for guiding freedpowder to a desired location when the object is tilted. The powder guidemay comprise a chute or a funnel that is oriented when the mechanicalmanipulator tilts the object to guide the freed powder to the desiredlocation. The powder guide may comprise a receptacle, such as a box-likesection, for housing the object, the chute or funnel forming part of thereceptacle. The receptacle may confine the freed powder such that thefreed powder is delivered to an outlet of the chute or funnel. Thereceptacle may comprise a first opening of the chute or funnel and asecond opening arranged such that the object and build substrate can bepushed into the receptacle through the second opening by the buildplatform. The second opening may be closed by the build substrate whenthe build substrate is pushed into the receptacle by the build platform.

The chute or funnel may be positionable when the object is titled by themechanical manipulator to dispense freed powder into the build volume,into a powder overflow channel and/or into a doser, such as a dosingpiston. In this way, the freed powder can be recovered for use in asubsequent build. The chute or funnel may be located in such a positionwhen the object has been inverted.

The powder bed fusion apparatus may comprise a powder overflow channeland/or a dosing piston and a sieve, wherein the sieve located orlocatable to sieve freed powder before it enters the powder overflowchannel and/or the dosing piston. The sieve may be movable. The sievemay be movable from a sieving position in which the sieve sieves freedpowder before it enters the dosing piston to a remote position such thatpowder raised above the working plane by operation of the dosing pistondoes not pass (back) through the sieve. The sieve may be movable from asieving position in which the sieve sieves freed powder before it entersthe powder overflow channel and/or dosing piston to a disposal positionin which material captured by the sieve is deposited in a collectionbin.

The mechanical manipulator may comprise a vibrator, such as anultrasonic vibrator, for vibrating the object when the object is tilted.

According to a second aspect of the invention there is provided abreak-out device for the break-out of an object from unsolidifiedpowder, the object built in a layer-by-layer manner in a powder bedfusion apparatus comprising a build platform movable within a buildsleeve to define a build volume, a layer formation device for forminglayers of powder across the build volume in a working plane and anirradiation device for irradiating powder in the working plane toselectively fuse the powder, the break-out device comprising amechanical manipulator arranged to be mounted in or on the powder bedfusion apparatus such that the mechanical manipulator can engage withthe object and/or a build substrate on which the object is built to tiltthe object when in a raised position above the working plane such thatpowder is freed from the object and deposited at a location above theworking plane and/or into the build volume.

The break-out device may be capable of being retrofitted to a powder bedfusion apparatus. The break-out device may comprise a build chamber doorfor a powder bed fusion apparatus, wherein the mechanical manipulator ismounted to the door, the door mountable on a build chamber of the powderbed fusion apparatus such that opening of the door moves the mechanicalmanipulator and an object retained by the mechanical manipulator fromthe build chamber.

Alternatively, the break-out device may be capable of being detachablymounted in or on the powder bed fusion apparatus for break-out of theobject. In the latter case, the break-out device may bedetachable/removable from the powder bed fusion apparatus such that itcan be used with one or more further powder bed fusion apparatus. As thebreak-out device is used for break-out of the object and not during thebuild, sharing of the break-out device may allow for optimisation of theutility of the break-out device.

The mechanical manipulator may comprise a drive mechanism arranged toextend outside of a build chamber of the powder bed fusion apparatus,wherein application of a force to the drive mechanism operates themechanical manipulator. The drive mechanism may be manually operable ordriven by a motor.

According to a third aspect of the invention there is provided aplurality of powder bed fusion apparatus, each of the powder bed fusionapparatus for building an object in a layer-by-layer manner andcomprising a build platform movable within a build sleeve to define abuild volume, a layer formation device for forming layers of powderacross the build volume in a working plane and an irradiation device forirradiating powder in the working plane to selectively fuse the powder,the plurality of powder bed fusion apparatus further comprising amechanical manipulator movable between the plurality of powder bedfusion apparatus such that, in each powder bed fusion apparatus, themechanical manipulator is capable of engaging with the object and/or abuild substrate, to which the object is attached, to tilt the object ina raised position above the working plane such that powder is freed fromthe object and deposited at a location above the working plane and/orinto the build volume.

According to a fourth aspect of the invention there is provided a powderbed fusion apparatus for building an object in a layer-by-layer manner,the powder bed fusion apparatus comprising a build platform movablewithin a build sleeve to define a build volume, a layer formation devicefor forming layers of powder across the build volume in a working plane,an irradiation device for irradiating powder in the working plane toselectively fuse the powder, a build chamber for maintaining an inertatmosphere surrounding the working plane and a movable transfer chambercomprising an aperture, wherein the transfer chamber is movable from afirst position in which the aperture is in communication with the buildchamber to allow transfer of the object into the transfer chamber and asecond position in which the object can be transferred from the transferchamber through the aperture into an ambient atmosphere.

The transfer chamber may be slidable between the first and secondpositions. Alternatively or additionally, the transfer chamber may berotatable between the first and second positions.

The powder bed fusion apparatus may comprise means for generating aninert atmosphere in the transfer chamber before bringing the aperture ofthe transfer chamber into communication with the build chamber.

An aperture may be provided in a ceiling of the build chamber whereinthe object can be transferred through this aperture into the transferchamber. The irradiation device may be movable and the irradiationdevice and the transfer chamber arranged such that either one of thetransfer chamber and the irradiation device may be located at theaperture in the ceiling of the build chamber. The irradiation device andthe transfer chamber may be movable together as a single module.

The apparatus may comprise a mechanical manipulator arranged to engagewith the object and/or a build substrate to transfer the object toand/or from the powder transfer chamber. The mechanical manipulator maybe retractable into the transfer chamber so as to be transportedtherein.

According to a fifth aspect of the invention there is provided a powderbed fusion apparatus for building an object in a layer-by-layer manner,the powder bed fusion apparatus comprising a build platform movablewithin a build sleeve to define a build volume, a dosing piston movablewithin a dosing sleeve for dosing powder, a wiper for spreading powderdosed from the dosing sleeve for forming layers of powder across thebuild volume in a working plane, an irradiation device for irradiatingpowder in the working plane to selectively fuse the powder and a sievemovable from a sieving position in which the sieve sieves freed powderbefore it enters the dosing piston to a remote position.

The remote position may be such that powder raised above the workingplane by operation of the dosing piston does not pass (back) through thesieve. The remote position may be a disposal position in which materialcaptured by the sieve is deposited into a collection bin.

According to a sixth aspect of the invention there is provided abreak-out device for the break-out of an object from unsolidifiedpowder, the object built in a layer-by-layer manner in a powder bedfusion apparatus comprising a build platform movable within a buildsleeve to define a build volume, a layer formation device for forminglayers of powder across the build volume in a working plane and anirradiation device for irradiating powder in the working plane toselectively fuse the powder, the break-out device comprising amechanical manipulator comprising a frame having coupling membersthereon for engaging with the object and/or a build substrate on whichthe object is built, the frame rotatable to tilt the object such thatpowder is freed from the object, the coupling members arranged such thatraising of the build platform with the object and/or build substratemounted thereon causes the coupling members to engage the object and/orbuild substrate.

The mechanical manipulator may be mountable in or on the powder bedfusion apparatus.

Alternatively, the mechanical manipulator may be mounted in or on abreak-out module separate from the powder bed fusion apparatus, thebreakout module comprising a space for receiving a removable buildsleeve of a powder bed fusion apparatus, the coupling members positionedor positionable such that raising of the build platform, with the objectand/or build substrate mounted thereon, when the build sleeve isreceived in the space within the break-out module causes the couplingmembers to engage the object and/or build substrate. Rotation of theframe within the break-out station may cause freed powder to fall backinto the build sleeve. The build sleeve contained freed powder may thenbe returned to the powder bed fusion apparatus for a subsequent build.The build sleeve may be useable as a dosing piston in the subsequentbuild.

According to a seventh aspect of the invention there is provided apowder bed fusion system comprising:

-   -   a powder bed fusion apparatus for building an object in a        layer-by-layer manner, the powder bed fusion apparatus        comprising a build chamber housing a build platform movable        within a build sleeve to define a build volume, a layer        formation device for forming layers of powder across the build        volume in a working plane, an irradiation device for irradiating        powder in the working plane to selectively fuse the powder, a        build chamber aperture in the build chamber for the removal of        the object rom the build chamber and a build chamber door for        closing the aperture;    -   a transfer chamber having a transfer chamber aperture for        receiving the object and a transfer chamber door for closing        transfer chamber aperture, the transfer chamber arranged to be        detachably mountable to the powder bed fusion apparatus to        register the transfer chamber aperture with the build chamber        aperture; and    -   a transfer device located in the powder bed fusion apparatus or        the transfer chamber and arranged to engage with the object        and/or a build substrate, to which the object is attached, to        transfer the object in a raised position above the working plane        from the build chamber into the transfer chamber.

In this way, the object can be transferred from the powder bed fusionapparatus to a location for further processing within the transferchamber in an inert atmosphere and/or such that powder remaining on theobject is contained within the transfer chamber. By transferring theobject in a raised position above the working plane from the buildchamber into the transfer chamber, a majority of the powder will remainwithin the powder bed fusion apparatus. The transfer chamber may bedetachably mountable to the powder bed fusion apparatus to seal aninterface between the transfer chamber and the powder bed fusionapparatus to leakage of powder and/or inert gas therefrom.

The transfer chamber door may seal the transfer chamber aperture suchthat an inert atmosphere can be maintained within the transfer chamber.The transfer chamber may comprise means to form an inert gas atmospheretherein before opening the transfer chamber to the atmosphere within thebuild chamber. For example, the transfer chamber may comprise a gascircuit detachably connectable to a gas circuit on the powder bed fusionapparatus such that inert gas can be supplied to the transfer chamberfrom the powder bed fusion apparatus. Alternatively, the transferchamber may comprise its own supply of an inert gas.

The transfer device may comprise a mechanical manipulator of the firstaspect of the invention which can be displaced from a first positionwithin the build chamber to a second position within the transferchamber to transfer the object therebetween. The transfer device maycomprise telescopic arms for moving the mechanical manipulator betweenthe two positions.

Alternatively, the transfer device may comprise a device separate from amechanical manipulator in the powder bed fusion apparatus for freeingpowder form the object, such as described with reference to the firstaspect of the invention, the transfer device arranged to take the objectfrom the mechanical manipulator and transfer the object into thetransfer chamber.

The transfer chamber may comprise a trolley for moving the transferchamber about a factory floor. The transfer chamber may comprise handlessuch that the transfer chamber can be manually pushed about the factoryfloor.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of part of a powder bed fusion apparatusaccording to a first embodiment of the invention, wherein a mechanicalmanipulator is in a position such that layers of powder can besolidified;

FIG. 2 is a perspective view of the powder bed fusion apparatus shown inFIG. 1 with the mechanical manipulator in a position for attaching to abuild substrate on which an object (not shown) has been built;

FIG. 3 is a perspective view of a flange on the build substrate and theconnecting formations on the mechanical manipulator;

FIG. 4 is a perspective view of the mechanical manipulator in a positionin which an object (not shown) attached to the build substrate isinverted by 180 degrees;

FIG. 5 is a perspective view of the mechanical manipulator in a positionin which an object (not shown) attached to the build substrate isinverted by an angle between 90 and 180 degrees;

FIG. 6 is a perspective view of the powder bed fusion apparatus showingthe outer doors to a build chamber;

FIG. 7 is a schematic view of a powder bed fusion apparatus according toa second embodiment of the invention;

FIG. 8 is a perspective view within a lasing chamber of the powder bedfusion apparatus shown in FIG. 7 ;

FIG. 9 shows the method of freeing unsolidified powder from the objectusing a receptacle of the mechanical manipulator of the apparatusaccording to the second embodiment of the invention;

FIG. 10 is a perspective view of the powder bed fusion apparatus of FIG.7 showing tilting of the sieve for disposal of oversized material;

FIG. 11 is a perspective view of a plurality of powder bed fusionapparatus according to the second embodiment of the invention, stackedside-by-side;

FIG. 12 is a schematic view of a powder bed fusion apparatus accordingto a third embodiment of the invention;

FIG. 13 a perspective view within a lasing chamber of the powder bedfusion apparatus shown in FIG. 12 ;

FIGS. 14 a to 14 c are side views and a perspective view of an end ofthe powder bed fusion apparatus in which an object built using theapparatus is stored for collection by an operator;

FIGS. 15 to 17 show a mechanical manipulator according to anotherembodiment of the invention in three different conditions;

FIG. 18 shows a powder bed fusion apparatus according to anotherembodiment of the invention;

FIG. 19 a is a perspective view of a top portion of a build piston ofthe powder bed fusion apparatus shown in FIG. 18 ;

FIG. 19 b is a sectional view through the build piston showing the drivemechanism for raising and lowering connecting pins;

FIG. 19 c is a perspective view of the build piston with the buildplatform in a lowered position and the connecting pins in a raisedposition;

FIG. 19 d is a perspective view of the build piston with the buildplatform in a lowered position and the connecting pins in a loweredposition;

FIG. 20 is a perspective view of a top portion of a build piston withthe build platform in a lowered position and the connecting pins in araised position and connected to the build substrate;

FIG. 21 is a top view of the powder bed fusion apparatus of FIG. 18illustrating various stages of opening the door; and

FIG. 22 is a perspective view of a transfer chamber according to anotherembodiment of the invention.

DESCRIPTION OF EMBODIMENTS

Referring to FIGS. 1 to 6 , a powder bed fusion apparatus 101 accordingto one embodiment of the invention comprises a build platform 102movable within a build sleeve 103 to define a build volume, a layerformation device (not shown) for forming layers of powder across thebuild volume in a working plane and an irradiation device (not shown)for irradiating powder in the working plane to selectively fuse thepowder. Successive formation of powder layers forms a powder bed in thebuild volume. The powder formation device typically comprises a doser(not shown) for dosing powder and a wiper (not shown) for spreading thedosed powder into a layer. In this embodiment, the doser is a top-doser,which doses powder onto surface 104.

A build chamber 113 is provided for maintaining an inert atmospheresurrounding the working surface of the powder bed. The build chamber 113may comprise an upper and lower chamber as described in WO2010/007394.Doors 111 a and 111 b provide access to each of the upper and lowerchambers of the build chamber, respectively. Gas flow inlet 114 and gasoutlet 115 are provided for generating an inert gas flow across theworking plane.

The doser may be in accordance with that disclosed in WO2010/007396. Alower edge of the wiper defines the working plane and is substantiallyaligned with the surface 104. The surface comprises apertures 117 a, 117b, which define channels for collecting powder. The channels 117 a, 117b lead to a collection hopper mounted to the side of build chamber 113via conduits 119 a, 119 b. Powder in the collection hopper can be reusedin a subsequent build and may be returned to the top-doser using anappropriate powder transport mechanism. Sloping side elements, in thisembodiment, in the form of wedge shaped elements 118 a, 118 b, areprovided either side of the build volume. The wedge shaped elements 118a, 118 b help to confine the powder to the area therebetween.

The powder bed fusion apparatus further comprises a mechanicalmanipulator 105 arranged to engage with a build substrate 106, to whichthe object is attached, to tilt the object in a raised position abovethe working plane such that powder is freed from the object anddeposited at a location above the working plane and into the buildvolume.

The mechanical manipulator 105 comprises an effector comprising a rigidframe comprising two L-shaped arms 107 a, 107 b connected together byconnecting members 108 a, 108 b. The frame surrounds an open space suchthat for at least one position of the effector, such as the positionshown in FIG. 1 , a laser beam of the irradiation unit can be directedto all parts of a surface of the powder bed without impinging on theframe. In this position, the effector also avoids interference with thegas flow generated across the working plane. The effector furthercomprises displaceable hook-shaped coupling members 109 a to 109 d thatare biased towards the position shown in FIG. 3 . The coupling members109 a to 109 d are arranged to hook under flanges 110 a, 110 b on thebuild substrate 106. The effector is mounted to the door 111 a via aspindle (not shown) such that the effector can rotate through 360degrees about an axis 112. The spindle extends through the door 111 aand extends outside of the build chamber, wherein application of a forceto the spindle rotates the effector. In this embodiment, the spindle isdriven by a motor (not shown) housed in motor housing 116. However, inan alternative embodiment, the spindle may be manually rotated, forexample via a lever or a wheel.

In use, during the building of an object, the effector is positioned asshown in FIG. 1 and an object is built in the conventional mannerlayer-by-layer by repeatedly lowering the build platform 102, spreadinga layer of powder across the build volume and solidifying selected partsof the layer using the irradiation device. After formation of a layer,any excess powder is pushed into collection channels 117 a, 117 b by thewiper. The object will typically comprise a part or workpiece to bebuilt and supports or anchors, which attach the part or workpiece to thebuild substrate 106. However, it is also known to build the part orworkpiece directly on the build substrate 106, for example as describedin EP1521657.

After the object has been completed, the effector is rotated to theposition shown in FIGS. 2 and 3 with arms 107 a, 107 b and couplingmembers 109 a to 109 d located just above the surface 104 either side ofthe build volume. The build platform 102 is then raised such thatflanges 110 a, 110 b on the build substrate 106 carrying the objectengage with and deflect coupling members 109 a to 109 d with thecoupling members returning under the biasing to the position shown inFIG. 3 once each flange 110 a, 110 b has moved past the hook shapedportions of the corresponding coupling members 109 a to 109 d. In thisposition, the build substrate 106 is retained by the effector.

With the build substrate 106 retained by the effector, the buildplatform 102 is lowered in the build sleeve 103. The effector is thenrotated by the motor to a completely inverted position shown in FIG. 4such that unsolidified powder is freed from the object and falls intothe build volume and/or onto surface 104. An ultrasonic vibrator (notshown) may be provided on or embedded within the effector, vibration ofthe effector and therefore, the build substrate 106 helping to freeunsolidified powder from the object.

To free unsolidified powder from internal tortuous channels within theobject it may be necessary to rotate the object to a number of differentorientations, with FIG. 5 showing one such position to which theeffector can be rotated.

At the end of a powder removal step, the effector is returned to theposition shown in FIG. 4 . The build platform 102 is then raised to pushthe freed unsolidified powder above the working plane with the wiperpushing the freed unsolidified powder into collection channels 117 a,117 b. Once the freed unsolidified powder has been recovered intochannels 117 a, 117 b, the door 111 a may be opened to extract theobject and build substrate 106 from the powder bed fusion apparatus. Theobject leaves the build chamber by virtue of being attached to themechanical manipulator, which is attached to the door 111 a. Theeffector may be rotated to orient the object in its as built orientationfor extraction, for example, for placing on a trolley for removal. Areplacement build substrate can then be placed on the build platform 102for the next build.

In an alteration to the above described embodiment, the mechanicalmanipulator may be mounted on a wall of the build chamber rather thandoor 111 a.

FIGS. 7 through 10 show a powder bed fusion apparatus according toanother embodiment of the invention. Features of this embodiment thatare the same or similar to features of the embodiment described withreference to FIGS. 1 to 6 have been given the same reference numeralsbut in the series 200.

In this embodiment, the doser 220 comprises a dosing piston 220 amovable in dosing sleeve 220 b. Powder is dosed from the dosing sleeve220 b by upwards movement of the dosing piston 220 a. A wiper 221spreads the powder elevated to above the working plane across the buildvolume defined by build sleeve 203.

A ceiling 213 a of the build chamber 213 comprises an aperture 222. Theirradiation device, in this embodiment, an optical module 223, andmechanical manipulator 205 are slidably mounted on a guide rail abovethe build chamber 213 such that each of the irradiation device 223 andthe mechanical manipulator 205 can be located above the aperture 222.When the irradiation device 223 is located above the aperture 222, themechanical manipulator is located above a part and build substratestorage area 224. When the mechanical manipulator 205 is located abovethe aperture 222, the irradiation device is located in irradiationdevice storage area 225. The mechanical manipulator 205 and irradiationdevice 223 may be driven between these positions by a motor. Alignmentmechanisms (not shown) may be provided for aligning the irradiationdevice 223 and mechanical manipulator 205 relative to the aperture 222,for example, a kinematic mount for locating the irradiation device 223and mechanical manipulator 205 in repeatable positions. The irradiationdevice 223 may be calibrated for scanning the working plane for thisrepeatable position.

The mechanical manipulator 205 is housed in a transfer chamber 271. Thetransfer chamber 271 is movable from a position located above theaperture 222 to a position above the storage area 224. The transferchamber 217 may form a seal with the ceiling wall such that objects canbe transferred into the mechanical manipulator without compromising theinert atmosphere in the build chamber 213.

The mechanical manipulator comprises a box-like receptacle 207 having anopening 229 at one end that matches the size and shape of the buildsubstrate 206 and, at the other end, a powder guide in the form of afunnel 232 for guiding freed powder to a smaller opening 226, whichprovides means for localising dispense of freed powder.

The box-like receptacle 207 is mounted for rotation on two extendiblearms 227, 228. Extension of the arms moves the receptacle 207 from araised position in the transfer chamber 271 above aperture 222 to alowered position, in which the receptacle can engage with a buildsubstrate 206 raised to a position above the working plane throughmovement of the build platform 202. The arms 227, 228 comprisetelescopic arrangements such that the arms 227, 228 can be extended andretracted to move the receptacle 207 between the two positions. Like theembodiment shown in FIGS. 1 to 6 , the receptacle may comprise couplingmembers/fingers thereon for engaging with a flange of the buildsubstrate 206.

In an unloading position of the manipulator 205 shown in FIG. 7 , thearms 227, 228 can lower the build substrate 206 and object attachedthereto to the storage area 224. The clean storage area 224 isaccessible via a door 242. A detachable filter assembly 231 forfiltering condensate and other particles from recirculated gas, forexample, as is described in WO2010/026396, is also accessible throughdoor 242 such that the filter assembly can be detached for replacementof the filter element. FIG. 8 illustrates gas flow inlets 214 and 215 inthe build chamber.

A movable sieve 233 is provided in the build chamber above the doser220. The sieve 233 is movable from a storage position spaced above theworking plane such that the wiper 221 can move below the sieve 233 tospread powder dosed by the doser 220 across the powder bed to a sievingposition in which the sieve 233 is received in the dosing sleeve 220 b.In this position, freed powder pushed back into the dosing sleeve 233passes through the sieve 233 such that large particulates are trapped bythe sieve 233. The sieve 233 is supported by two arms 234 and 235movable in slots 236, 237. Simultaneous raising and lowering of the arms234, 235 raises and lowers the sieve 233, whereas, as shown in FIG. 10 ,raising of one of the arms 236 simultaneously with lowering of the otherarm 237 tips the sieve 233 such that trapped particulates are dispensedinto an oversize particle disposal channel 238.

In use, during the building of an object 270, the optical module 223 ispositioned above the aperture 222, as shown in FIGS. 7 and 8 . Theoptical module 223 directs a laser beam to selected locations in theworking plane through window 275. At the end of the build, the opticalmodule 223 is retracted and the mechanical manipulator 205 is positionedabove the aperture 222.

The mechanical manipulator 205 is then controlled to lower thereceptacle 207 into the build chamber and engage working surface 204.During this operation, the powder and object remain within the buildvolume. Once the receptacle 207 has been lowered in place, the buildplatform 202 is raised to push the unsolidified powder and object intothe receptacle 207. The walls of the receptacle 207 confine the powderto the enclosed volume. The build platform 202 is raised until theflange on the build substrate 206 engages with the coupling members onthe receptacle 207. The receptacle 207, which contains the object and towhich the build substrate 206 is attached, is rotated above the workingplane to free powder from the object and to direct the opening 226downwards such that unsolidified/freed powder is dispensed from thereceptacle back into the build volume. Before and/or during rotation ofthe receptacle 207, the build platform 202 is lowered such that freedpowder can be collected within the build volume.

The mechanical manipulator may also comprise a vibrating mechanism, suchas an ultrasonic vibrator for vibrating the receptacle 207 duringrotation to facilitate the movement of powder to the opening 226.

A controller for controlling the apparatus may be pre-programmed to movethe receptacle 207 through a sequence of movements (rotations and linearmovements) based upon the internal geometry of the object. For example,a particular sequence of movements may aid the freeing of powder frominternal passageways and may be determined based upon the geometry ofthose internal passageways.

After the operation to recover powder into the build volume, thereceptacle 207 is lifted out through aperture 222 and moved to theposition shown in FIG. 7 .

To recover the powder dispensed into the build volume back into thedoser 220, the sieve 233 is lowered into the doser sleeve 220 b. Thebuild platform 202 is then raised and the wiper 221 actuated to pushpowder raised above the working plane on-top of the sieve 233. Particlesof the powder that are not oversize fall into the doser sleeve 220 bwhereas oversize particles are captured by the sieve 233. As shown inFIG. 10 , at suitable times, the sieve 233 can be titled to dispense theover-size particles collected thereon into the oversize powder channel238. The oversize particles are collected in oversize particlecollection hopper 239 for removal by a user.

The mechanical manipulator 205 lowers the finished object which isattached to the build substrate 206 to the clean storage area 225 forremoval by a user and picks up a new build substrate 206′. Themechanical manipulator 205 is then operated to transfer the new buildsubstrate 206′ to the build platform 202 for a subsequent build. The newbuild substrate 206′ is stored in a suitable location in order that itcan be picked up by the mechanical manipulator 205 once the object andassociated build substrate have been dropped off in the storage area225.

Top-ups to the powder in the doser 220 can be made through powder inlet240. In FIG. 7 , a powder canister 241 is shown attached to the powderinlet 240.

Referring to FIG. 11 , as routine servicing operations, such as removalof finished objects, removal and replacement of the filter assembly 231,access to the powder inlet 240 and removal of the oversize powder hopper239, can be carried out through access doors located at opposed ends ofthe apparatus, a plurality of the apparatus may be stacked togetherside-by-side in a row. This helps to reduce the floor space occupied bythe plurality of apparatus compared to current machines, which preventsuch stacking of the apparatus at least due to access requirements. Eachmachine may be mounted on floor rails such that on occasions when accessto the build chamber is required, for example during a material changeor for servicing, the machine can be pulled out from the row ofapparatus into a central corridor for cleaning. Side access doors 243 to248 are provided for these occasional operations.

FIGS. 12 through 14 show a powder bed fusion apparatus according toanother embodiment of the invention. Features of this embodiment thatare the same or similar to features of the embodiment described withreference to FIGS. 7 to 11 have been given the same reference numeralsbut in the series 300.

This embodiment differs from the previous embodiment in that theoversize powder hopper 339 and powder inlet 340 are provided at the sameend of the apparatus as the object clean storage area 324 and the filterassembly 331. Accordingly, access to only one end of the apparatus isrequired for the routine servicing operations.

The sieve 333 is mounted on arms that move in slots 336, 337 in an endwall of the build chamber 313 rather than a side wall. The wiper 321 ismounted on rails located above the build chamber 313.

The object clean storage area 324 comprises a support, in thisembodiment in the form of support platform 350, for supporting thecompleted object and the build substrate 306. The support platform 350is mounted on a linear axis such that support platform 350 can be movedto a receiving position for receiving the object and associated buildsubstrate 306 from the mechanical manipulator 305 and a build substratepick-up position, in which the mechanical manipulator can pick up areplacement build substrate 306′ from the support platform 350. Movementof the support platform is driven by motor 351.

With the apparatus according to this embodiment only requiring accessfrom one end during routine operations, a plurality of such apparatuscan be stacked side-by-side and back-to-back.

FIGS. 15 to 17 shows a mechanical manipulator 405 according to anotherembodiment of the invention. Features of this embodiment that are thesame or similar to features of the above described embodiments have beengiven the same reference numerals but in the series 400.

The mechanical manipulator 405 may be used in apparatus, such asdescribed with reference to FIGS. 7 to 14 . In this embodiment, themechanical manipulator 405 can simultaneously hold both the object 450and the substrate 406 to which it is attached and a replacementsubstrate 406′ to be used for a subsequent build. Rotation of arms 407a, 407 b of the mechanical manipulator frees powder from the object andallow build substrate 406′ to be located on the build platform 402 for asubsequent build.

The mechanical manipulator 406 comprises cantilevered arms 427, 428movable along guide rails 459 a, 459 b. Linkages in the form of levers451, 452 are mounted on the cantilevered arms 427, 428 to be rotatableabout a corresponding axis. One end of each lever 451, 452 is connectedto a threaded follower 456 by linkages 457, 458. Each linkage 457, 458is pivotable about joints to the corresponding lever 451, 452 and thefollower 456. The follower 456 is threaded on a screw-thread 454,wherein rotation of the screw thread driven by motor 455 drives thefollower 456 along the screw-thread 454.

Connected to the other end of the levers 451, 452 is an end effector inthe form of two gripper fingers 460, 461. Each gripper finger 460, 461is rotatably mounted on the corresponding lever 451, 452 and rotation ofthe gripper is driven by gripper motor 462. Each gripper finger 460, 461comprises a first coupling members 460 a, 461 a for engaging with afirst build substrate 406 and a second coupling members 460 b, 461 b forengaging with a second, replacement build substrate 406′.

In use, on completion of a build, the build platform is operated toraise the object and build substrate 406 to the top of the build sleeve.The mechanical manipulator is moved in place above the aperture in theceiling of the build chamber. Held within coupling members 460 b and 461b of the gripper is a replacement build substrate 406′. The replacementbuild substrate 406′ is held in the top, inverted position shown in FIG.15 . Motor 455 is operated to rotate the screw thread 454 movingfollower 456 downwards. This first pulls linkages 457, 458 to theposition shown in FIG. 15 . The angle of the linkages 457, 458 pulls thetop ends of the levers 451, 452 together pulling coupling members 460 a,461 a apart whilst coupling members 460 b, 461 b retain a grip on thereplacement build substrate 406′. Further movement of the follower 456pulls moves the cantilevered arms 427 along the guide rails 459 a, 459b.

The gripper is lowered to locate the coupling members 460 a, 461 aeither side of the build substrate 406 on which the object has beenbuilt. The drive from motor 455 is then reversed driving the follower456 up the screw thread 454 straightening linkages 457 and 458 to pushthe coupling members 460 a, 461 a together to grip the build substrate406, as shown in FIG. 16 . Gripper motor 462 is then driven to rotatethe gripper and locate the replacement build substrate 406′ adjacent thebuild platform whilst simultaneously inverting the build substrate 406and the object to free powder still attached thereto. The follower 456can then be driven down again to open the coupling members 460 b, 461 bto release the replacement build substrate on to the build platform 402,as shown in FIG. 17 . The follower 456 is then driven upwards to liftthe mechanical manipulator together with the object out of the buildchamber, and the object can be carried to and deposited in a storagelocation as described above with reference to FIGS. 7 to 14 . During thedepositing of the object in the storage location, a further replacementbuild substrate may be picked up.

A further embodiment of the invention is shown in FIGS. 18 to 21 .Features of this embodiment that are the same or similar to features ofthe above described embodiments have been given the same referencenumerals but in the series 500. This embodiment is similar to theembodiment described with reference to FIGS. 1 to 6 with a door 511 amounted mechanical manipulator 505.

This embodiment differs from the embodiment described with reference toFIGS. 1 to 6 in that the build substrate 506 is secured to the buildplatform 502 during the build and a mechanism is provided for releasingthe build substrate 506 from the build platform 502 for tilting of thebuilds substrate 506 and object with the mechanical manipulator 505.

The mechanical manipulator 505 comprises arms 507 a, 507 b having achannel therein for engaging with a flange on the build substrate 506.An actuating mechanism is movable within each channel for engaging witha locking member of the build substrate 506. In the embodiment, theactuating mechanism is activated by cable ties that extend outside ofthe build chamber 513 such that the actuating mechanism can be operatedby a drive located externally to the build chamber. However, in anotherembodiment, the actuating mechanism may be driven by a drive locatedwithin the build chamber, such as an electromagnet.

The build substrate 506 comprises an internal channel 580 in which alocking member 581 is movably located. In this embodiment, the buildplate 506 is formed from a lower plate 506 a having the recess cuttherein for the forming the internal channel 580, locking member 581 andan upper plate 506 b. The lower plate has three holes therein forreceiving lugs of connecting pins 583 a, 583 b, 583 c. The lockingmember 581 is movable within the channel from a position in which itengages the lugs to a position disengaged from the lugs under thecontrol of the actuating mechanism located on the mechanical manipulator505.

As best shown in FIGS. 19 a to 19 d , the build piston comprisesconnecting pins 583 a, 583 b, 583 c that move with the build platform502 but can also be driven to extend from the build platform 502. Asmost clearly shown in FIG. 19 b , the movement of the connecting pins583 a, 583 b, 583 c relative to the build platform 502 is driven by abelt drive mechanism located below the build platform 502. A motor 584drives a belt 585 around a loop to turn threaded members 586 a, 586 b,586 c. The treaded members 586 a, 586 b, 586 c engage complimentarythreads on connecting pins 583 a, 583 b, 583 c to move the connectingpins 583 a, 583 b, 583 c relative to the build platform 502.

In use, the build substrate is attached to the connecting pins 583 a,583 b, 583 c and, during the build, the build platform 502 is loweredtogether with the connecting pins 583 a, 583 b, 583 c to allow theobject to be formed layer-by-layer. However, unlike the embodimentdescribed with reference to FIGS. 1 to 7 , at the end of the build, thebuild platform 502 remains at a lower position in the build sleeve 503,as shown in FIG. 20 , whilst the pins are driven to move the buildsubstrate upwards to the top of the build sleeve 503. During thistransition, powder will fall through the gap between the build substrate506 and the build sleeve 503 into the build volume. By the time thebuild substrate 506 has been raised to the top of the build piston, themajority of the unsolidified powder surrounding the object will havefallen back into the build volume. Accordingly, when the flanges on thebuild substrate 506 engage with the mechanical manipulator 505, in theposition shown in FIG. 20 , these regions are substantially free ofpowder which could inhibit the connection of the build substrate 505 tothe mechanical manipulator 505.

The actuating mechanism is then driven to decouple the build substrate506 from the connecting pins 583 a, 583 b, 583 c and the mechanicalmanipulator 505 rotated to tilt the object, freeing powder that wascaptured within the object. This embodiment may reduce an amount ofpowder that is deposited outside of the build volume reducing the weightof powder to be moved by the wiper to the overflow channels in aninitial powder clearance stroke. The amount of powder to be pushed bythe wiper into the overflow channels on subsequent powder clearancestrokes can be controlled by an amount the build platform is raisedbetween strokes.

FIG. 21 shows a pivot mechanism 590 for attaching the mechanicalmanipulator 505 to the door 511 a. The pivot mechanism 590 allows themechanical manipulator to pivot about in an axis in a direction oppositeto a direction the door 511 a pivots about its axis such that themechanical manipulator 505 can be moved from the build chamber 513without contacting a wall of the build chamber 513.

It will be understood that alterations and modifications may be made tothe above described embodiments without departing from the invention asdefined herein. For example, rather than a dosing piston the doser maybe a “top” doser which doses powder from above onto the surface 104,204, 304. Powder may be transferred to the top doser from above andrather than depositing the freed powder back into the build volume, thereceptacle may be moved to a location in which the freed powder can berecovered to a hopper of the top doser. This inlet may be accessiblefrom the storage area allowing the user to top up powder into the topdoser and for servicing of a sieve that filters the recovered powder asit is reintroduced into the top doser from the receptacle. Use of a topdoser may allow the apparatus to have a smaller footprint and overcome aproblem with dosing pistons in that a volume of the dosing piston has tobe greater than the build volume due to packing of the powder and/orshrinkage of the solidified material during the build.

The receptacle may also be used during a material changeover. Inparticular, during a material change, the powder may be pushed into thebuild volume on top of the build substrate using the wiper. Thereceptacle may be then lowered in place and the powder pushed into thereceptacle by raising the build substrate, as described above, until thebuild substrate engages the coupling members on the receptacle. Ratherthan rotating the receptacle, the receptacle could then be lifted fromthe build chamber thus extracting the powder. A replacement receptaclecontaining the replacement powder could then be carried to the buildchamber by the mechanical manipulator and the replacement powderdeposited in the build volume. Rather than using the same receptacle formaterial change, a receptacle having a closed top may be used to ensurethat the powder is not exposed to oxygen when the powder is removed fromthe inert atmosphere in the build chamber. Alternatively, a system maybe provided to cap the narrow opening in the receptacle. Furthermore,the powder may be removed from the build chamber together with theobject rather than in separate operations.

In an alternative embodiment, the mechanical manipulator of any of theabove described embodiments is transferrable between a plurality ofpowder bed fusion apparatus such that it can be used in the break-out ofobjects from the powder in each machine. In the case of the embodimentsdescribed with reference to FIGS. 7 to 14 , it may be the case that theentire mechanical manipulator is transferrable, for example theactuating/handling mechanism and the receptacle 207, 307, or only theactuating/handling mechanism may be transferrable with the receptacles207, 307 being left in the machine to which they are dedicated. Nottransferring the receptacle may help to prevent cross-contamination ofpowder between machines.

In a further embodiment, the mechanical manipulator may be provided in abreak-out module separate from the powder bed fusion. The build sleeve103 and build platform 102 may form together a container that isremovably mounted in the powder bed fusion apparatus. The breakoutmodule comprises a space for receiving the removable container of apowder bed fusion apparatus such that raising of the build platform 102to the top of the build sleeve 103 causes the build substrate 106mounted thereon to engage with the coupling members on the mechanicalmanipulator. The removable container may be removable together with theelevator mechanism for moving the build platform in the build sleeve oreach of the powder bed fusion apparatus and the break-out module mayhave an elevator mechanism fixed therein which engages with the buildplatform to move the build platform.

Rotation of the frame of the mechanical manipulator within the break-outstation causes unsolidified powder to fall back into the containerformed by the build sleeve and build platform. The build sleeve andbuild platform containing the freed powder may then be returned to thepowder bed fusion apparatus for a subsequent build. In this way, if theobject should remain in the powder for some time as it cools, thiscooling process can take place in the break-out module, freeing up thepowder bed fusion apparatus to carry out the next build.

A further embodiment of the invention is shown in FIG. 22 . Features ofthis embodiment that are the same or similar to features of the abovedescribed embodiments have been given the same reference numerals but inthe series 600.

In this embodiment, the transfer chamber 671 is a separate module fromthe powder bed fusion apparatus and detachably mountable to the powderbed fusion apparatus 601. The transfer chamber 671 is mounted on atrolley and brought into mating contact with the powder bed fusion toform a seal around an opening in the build chamber through which theobject is passed. A manually operated handle 691 may be provided, which,when operated, forces the transfer chamber 671 against the side of thepowder bed fusion apparatus 601 to form the seal. A gas inlet 693 may beprovided for connecting the transfer chamber 671 to an inert gas supplyof the powder bed fusion apparatus 601. If an inert atmosphere is to beformed in the transfer chamber 671 then this is done before the door(not shown) to the transfer chamber 671 and the door 695 to the buildchamber is opened. The formation of an inert atmosphere may be carriedout to avoid the inert atmosphere in the build chamber being compromisedand/or to allow cool down of the object within an inert atmosphere.However, it may be deemed acceptable to compromise and therefore, havingto reform, the inert atmosphere in the build chamber between builds andthe main purpose of the transfer chamber is for the removal and transferof the object in a manner that reduces the release of powder into thesurrounding environment.

To remove the object, the door to the transfer chamber 671 and the door695 to be build chamber are opened and the object transferred into thetransfer chamber 671 from the build chamber. The transfer device fortransferring the object may comprise the mechanical device as describedwith reference to FIGS. 1 to 6 , but mounted on a rear wall of the buildchamber by a telescopic arm. The telescopic arm is driven to extend themechanical manipulator holding the object into the transfer chamber 671.The object is then detached from the mechanical manipulator to leave theobject within the transfer chamber 671 on retraction of the mechanicalmanipulator.

The trolley reduces the physical load on the operator when removingheavy/cumbersome parts and removes the need for the operator to be inclose proximity to the build chamber.

The doors are then closed and the transfer chamber 671 can be wheeled ontrolley 694 to another location for further processing of the object.

In a further embodiment, a transfer device is provided within thetransfer chamber 671 for picking the object up from a mechanicalmanipulator within the powder bed fusion apparatus 601 and transferringthe object into the transfer chamber 671.

The invention claimed is:
 1. A powder bed fusion apparatus for buildingan object in a layer-by-layer manner, the powder bed fusion apparatuscomprising a build platform movable within a build sleeve to define abuild volume, the build platform for supporting a powder bed within thebuild volume, an irradiation device arranged to generate an energy beamand a scanner arranged to steer the energy beam to irradiate powder ofthe powder bed to selectively fuse the powder bed and a mechanicalmanipulator arranged to engage with the object and/or a build substrate,to which the object is attached, to tilt the object such that powder isfreed from the object, wherein the mechanical manipulator comprises anend effector positionable to receive the object and/or the buildsubstrate when conveyed from the build sleeve such that the objectand/or the build substrate attach to the end effector, whereinsubsequent movement of the end effector tilts the object.
 2. A powderbed fusion apparatus according to claim 1, wherein the mechanicalmanipulator is arranged to engage with the build substrate supported onthe build platform and on which the object is built and attached, themechanical manipulator arranged to tilt the object by virtue of tiltingthe build substrate.
 3. A powder bed fusion apparatus according to claim1, wherein the mechanical manipulator is arranged to invert the object.4. A powder bed fusion apparatus according to claim 1, wherein themechanical manipulator is arranged to rotate the object about two axes.5. A powder bed fusion apparatus according to claim 1, wherein themechanical manipulator is mounted in the apparatus such that the buildplatform has to be moved from an engagement position in which themechanical manipulator engages with the object and/or the buildsubstrate to provide room for rotation of the mechanical manipulatorengaged with the object and/or the build substrate.
 6. A powder bedfusion apparatus according to claim 1, comprising a chamber formaintaining an inert atmosphere surrounding the object during the build,wherein the mechanical manipulator is arranged to tilt the object withinthe chamber such that powder is freed from the object whilst under theinert atmosphere.
 7. A powder bed fusion apparatus according to claim 6,wherein the mechanical manipulator comprises a drive mechanism thatextends outside of the chamber, wherein application of a force to thedrive mechanism operates the mechanical manipulator.
 8. A powder bedfusion apparatus according to claim 1, wherein the end effectorcomprises at least one movable arm positionable such that raising of thebuild platform causes the object and/or the build substrate to beattached to the at least one arm, wherein subsequent movement of the atleast one arm tilts the object.
 9. A powder bed fusion apparatusaccording to claim 8, wherein the arm and the build substrate comprisecooperating fastening elements that are engaged to attach the mechanicalmanipulator to the build substrate by raising of the build platform. 10.A powder bed fusion apparatus according to claim 9, wherein thecooperating fastening elements comprise a resilient element on one ofthe arms of the manipulator and the build substrate that is deflected byengagement of a flange on the other of the build substrate and the armof the manipulator to cause the resilient element to grip the flange,thus attaching the mechanical manipulator to the build substrate.
 11. Apowder bed fusion apparatus according to claim 8, wherein the movablearm is mounted for rotation about an axis that is not orthogonal to theworking plane.
 12. A powder bed fusion apparatus according to claim 1,wherein the mechanical manipulator comprises a receptacle for housingthe object, the receptacle comprising a first opening through whichpowder can fall when the receptacle is in a required orientation whilstpowder cannot fall through the first opening when the receptacle isrotated to another orientation and a second opening for receiving thepowder and the object, the second opening arranged to be closed by thebuild substrate when the build substrate is engaged with the mechanicalmanipulator.
 13. A powder bed fusion apparatus according to claim 12,wherein the receptacle is a box-like receptacle for housing the object.14. A powder bed fusion apparatus according to claim 1, wherein themechanical manipulator comprises a raising and lowering device forraising and lowering the end effectors without rotation of the endeffectors.
 15. A powder bed fusion apparatus according to claim 14,wherein the raising and lowering device is for raising and lowering anaxis about which the mechanical manipulator rotates the end effectors.16. A powder bed fusion apparatus according to claim 12, wherein themechanical manipulator comprises a raising and lowering device forraising and lowering the receptacle.
 17. A powder bed fusion apparatusaccording to claim 1, wherein the mechanical manipulator comprisescoupling members for retaining a replacement build substrate, thecoupling members arranged such that the coupling members can be rotatedto locate the replacement build substrate adjacent to the buildplatform, the coupling members further arranged to release thereplacement build substrate on to the build platform.
 18. A powder bedfusion apparatus for building an object in a layer-by-layer manner, thepowder bed fusion apparatus comprising a build platform movable within abuild sleeve to define a build volume, the build platform for supportinga powder bed within the build volume, an irradiation device arranged togenerate an energy beam and a scanner arranged to steer the energy beamto irradiate powder of the powder bed to selectively fuse the powder bedand a mechanical manipulator arranged to engage with the object and/or abuild substrate, to which the object is attached, wherein the mechanicalmanipulator comprises an end effector positionable to receive the objectand/or the build substrate when conveyed from the build sleeve such thatthe object and/or the build substrate attach to the end effector, andcoupling members for retaining a replacement build substrate, the endeffector and the coupling members movable to move the object and/or thebuild substrate from a location adjacent to the build platform and tolocate the replacement build substrate to the location adjacent thebuild platform, the coupling members further arranged to release thereplacement build substrate on to the build platform.
 19. A powder bedfusion apparatus according to claim 18, wherein movement of the endeffector and the coupling members is caused by a common drive mechanism.20. A powder bed fusion apparatus according to claim 18, wherein the endeffector and the coupling members are arranged to rotate about a commonaxis.
 21. A break-out device for the break-out of an object fromunsolidified powder, the object built in a layer-by-layer manner in apowder bed fusion apparatus comprising a build platform movable within abuild sleeve to define a build volume, the build platform for supportinga powder bed within the build volume, an irradiation device arranged togenerate an energy beam and a scanner arranged to steer the energy beamto irradiate powder of the powder bed to selectively fuse the powderbed, the build sleeve movable from a build position in which the powderis fused, the break-out device comprising a space for receiving thebuild sleeve moved from the build position and a mechanical manipulatorcomprising a frame having coupling members thereon for engaging with theobject and/or a build substrate on which the object is built, the framerotatable to tilt the object such that powder is freed from the object,the coupling members positioned or positionable to receive the objectand/or the build substrate when conveyed from the build sleeve receivedin the space within the break-out device to cause the coupling membersto engage the object and/or the build substrate.
 22. A break-out deviceaccording to claim 21, wherein the mechanical manipulator is mountablein or on the powder bed fusion apparatus.
 23. A break-out deviceaccording to claim 21, wherein the mechanical manipulator is mounted inor on the break-out device separate from the powder bed fusionapparatus, wherein the space is for receiving a removable build sleeveof the powder bed fusion apparatus.
 24. A break-out device according toclaim 23, wherein rotation of the frame within the break-out devicecauses freed powder to fall back into the build sleeve.
 25. A break-outdevice according to claim 21, wherein the coupling members comprisehooks arranged to be pushed away when engaged by the build substrate asthe build substrate is conveyed from the build sleeve and biased to hookunder a portion of the build substrate to retain the build substrate inplace on the mechanical manipulator.